1. Field of the Invention
The present invention relates to an ink jet ink, an ink jet recording method, an ink cartridge, a recording unit and an ink jet recording apparatus.
2. Description of the Related Art
An ink jet recording method is a method of forming images by applying ink droplets to recording media such as plain paper and glossy media. This method has rapidly come into widespread use by the reduction in cost and improvement in recording speed of ink jet recording apparatuses. Further, with the rapid spread of digital cameras in addition to the progress in obtaining high-quality images by the ink jet recording method, the ink jet recording method has been commonly used as the output method of images equal to silver halide photographs.
In recent years, further progress in obtaining high-quality images is achieved by minimization of ink droplets and improvement in the color gamut accompanying introduction of a multicolor ink. On the other hand, the demand to a coloring material and ink becomes higher, wherein severer properties are demanded in the improvement in color developabilities and reliability of clogging and ejection stability.
On the other hand, it is mentioned that the ink jet recording method is inferior in the image storage stability of the obtained recorded matter, as a problem of the ink jet recording method. Generally, the image storage stability of the recorded matter obtained by the ink jet recording method is low as compared with silver halide photographs. When a recorded matter is specifically exposed to light, humidity, heat, the environmental gas that is present in the air, etc. for a long time, there is a problem that the coloring material on the recorded matter deteriorates and is easy to generate the change of color tone and fading of images.
Especially, from the viewpoint of the fastness of the images formed using a dye ink which contains a dye as a coloring material, particularly lightfastness, the lowness of the lightfastness accompanying a chemical reaction peculiar to the coloring material has been a subject. Many proposals have been made to solve the problem of this lightfastness to enhance the lightfastness of images. In particular, many proposals have been made with respect to a dye used for magenta ink, which has a low image storage stability in each ink of cyan, magenta and yellow.
For example, there are proposals on a xanthene dye and an azo dye using H acid as a coloring material which can form images excellent in image storage stability such as water resistance and color tone (Japanese Patent Application Laid-Open No. H08-073791 and Japanese Patent Application Laid-Open No. H09-255882). However, a xanthene dye is very excellent in color tone, but it is very inferior in lightfastness. On the other hand, an azo dye using H acid may have good color tone, but it is inferior in lightfastness and gas resistance. Although a study for developing a magenta dye excellent in color tone and lightfastness has been widely performed on these types of dye, it still cannot be said that the lightfastness level is enough as compared with a dye having other hues such as a cyan dye typified by copper phthalocyanine dyes and a yellow dye.
Further, there is a proposal on an anthrapyridone dye as a magenta dye excellent in color tone and lightfastness (Japanese Patent Application Laid-Open No. 2005-008868). However, a magenta dye satisfying clarity, gas resistance, and lightfastness equal to a dye having other hues is not yet obtained.
There are proposals on a magenta ink which can form images excellent in color tone, and ozone resistance and lightfastness by containing an anthrapyridone dye and an azo dye (Japanese Patent Application Laid-Open No. 2005-105136 and Japanese Patent Application Laid-Open No. 2005-307068). These proposals describe that a magenta ink which can form images excellent in both high gas resistance and lightfastness can be obtained by using an anthrapyridone dye with high gas resistance and low lightfastness together with an azo dye with low gas resistance and high lightfastness, thereby compensating mutual characteristics. However, although an image formed by such an ink containing both an anthrapyridone dye and an azo dye has gas resistance and lightfastness which have been improved to some extent as compared with an image formed by an ink containing only one of an anthrapyridone dye and an azo dye as a coloring material, the level of the fastness demanded in recent years is not reached.